Random Access Memory is a common form of computer data storage where data items are read and written in roughly the same amount of time regardless of the order in which data items are accessed. Integrated-circuit RAM chips have been available for several decades. Two main forms of RAM today are static RAM (SRAM) and dynamic RAM (DRAM). DRAM is less expensive and more common than SRAM. DRAM stores a bit of data using a memory cell comprising a transistor and capacitor pair. The cell holds a high charge (1) or a low charge (0). The transistor acts as a switch to change from a high charge to a low charge. Traditional storage systems and servers utilize CPUs with dedicated single-port DDR4, DDR3, or DDR2 DIMMs of DRAM. Additionally, many current storage systems and servers utilize dual-port serial attached SCSI (SAS) SSD devices or dual-port Non-Volatile Memory Express (NVME) SSD devices.
Double data rate fourth generation synchronous dynamic random-access memory (DDR4 DRAM) and non-volatile memory (NVM) technologies have been developed as single-port modules directly attached to a CPU. DDR4 provides a multi-channel architecture of point-to-point connections for CPUs hosting multiple high-speed DDR4-DIMMs rather than multi-drop DDR2/3 bus technologies. However, this technology has not been adopted yet, and the vast majority of DDR4 motherboards are still based on multi-drop bus topology. High density SSD storage systems and large-scale NVM systems need to use dual-port primary storage modules that are similar to higher reliability SAS-HDD devices for avoiding single-point failures along a data path. The greater the SSD/NVM density, the more critical the primary SSD/NVM device will be.
While high-end storage systems require dual-port DDR4-DIMM to improve system reliability and availability, current low-cost SDRAM, MRAM and ReRAM chips do not support DDR4 speed. What is needed is a dual-port DDR4-DIMM that improves system reliability and availability and also provides DDR4 speed with low speed memory chips.